e-ISSN 2231-8526
ISSN 0128-7680

Home / Regular Issue / JST Vol. 31 (3) Apr. 2023 / JST-3496-2022


The Effect of Preload, Density and Thickness on Seat Dynamic Stiffness

Azmi Mohammad Hassan, Khairil Anas Md Rezali, Nawal Aswan Abdul Jalil, Azizan As’arry and Mohd Amzar Azizan

Pertanika Journal of Science & Technology, Volume 31, Issue 3, April 2023


Keywords: Dynamic stiffness, seat cushion, seat dynamic, seat vibration

Published on: 7 April 2023

The vibration transferred to the car floor transmits to the human body through the seat structure, and the typical design of the seat structure consists of several components such as seat frame and seat cushion. The material widely used as seat cushion is open-cell polyurethane (PUR) foam; when under vibration, it will behave dynamically. Factors such as mechanical properties and material thickness of PUR can affect its behaviour and performance and the amount of vibration transmits to the human body. This work measures the PUR dynamic stiffness for different material densities and thicknesses. The test was conducted using an indenter head with a flat surface since it was a less expensive method, and quicker measurement could be done. The force sensor was placed within the indenter structure to measure the load transmitted to the seat and acceleration data acquired by the accelerometer, which was mounted on a shaker test plate. Foam materials with 30 kg/m3 and 44 kg/m3 with 30 mm and 50mm thickness are used in the experiment with the amount of preload applied of 20 N,30 N and 40 N. Seat stiffness increased when the preload increased from 20 N to 40 N, and a similar trend occurred when foam thickness decreased. The lower density of PUR resulted in a greater increase of seat stiffness and damping across the frequency 0-30 Hz compared to a higher density of PUR. This study concluded that thickness, preload, and density significantly affect seat dynamic stiffness.

  • Bang, J. H., Lee, C. A., Kim, H. Y., Kim, H. J., & Choi, K. Y. (2017). Optimization of the static properties of seat foam to improve the seating comfort. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 231(14), 1945-1960.

  • Choi, H. J., & Kim, J. H. (2020). Static and dynamic comfort properties of polyurethane foams including a flexible amine crosslinker. Journal of Industrial and Engineering Chemistry, 90, 260-265.

  • Deng, R., Davies, P., & Bajaj, A. K. (2003). Flexible polyurethane foam modelling and identification of viscoelastic parameters for automotive seating applications. Journal of Sound and Vibration, 262(3), 391-417.

  • Ebe, K., & Griffin, M. J. (2001). Factors affecting static seat cushion comfort. Ergonomics, 44(10), 901-921.

  • Griffin, M. J. (1990). Handbook of Human Vibration. Academic Press.

  • Kamp, I. (2012). The influence of car-seat design on its character experience. Applied Ergonomics, 43(2), 329-335.

  • Karen, I., Kaya, N., Öztürk, F., Korkmaz, I., Yildizhan, M., & Yurttaç, A. (2012). A design tool to evaluate the vehicle ride comfort characteristics: Modeling, physical testing, and analysis. International Journal of Advanced Manufacturing Technology, 60, 755-763.

  • Kreter, P. E. (1985). Polyurethane foam physical properties as a function of foam density. Journal of Cellular Plastics, 21(5), 306-310.

  • Murata, S., Ito, H., & Sopher, S. (2014). Polyurethane-free lightweight automotive seat. SAE International Journal of Materials and Manufacturing, 7(3), 655-661.

  • Patten, W. N., Sha, S., & Mo, C. (1998). A vibrational model of open celled polyurethane foam automotive seat cushions. Journal of Sound and Vibration, 217(1), 145-161.

  • Qiu, D., He, Y., & Yu, Z. (2019). Investigation on compression mechanical properties of rigid polyurethane foam treated under random vibration condition: An experimental and numerical simulation study. Materials, 12(20), Article 3385.

  • Tufano, S., & Griffin, M. J. (2013). Nonlinearity in the vertical transmissibility of seating: The role of the human body apparent mass and seat dynamic stiffness. Vehicle System Dynamics, 51(1), 122-138.

  • Wada, H., Toyota, Y., Horie, A., Sasaki, T., Suzuki, C., & Fukuda, H. (2008). Automotive seating foams with excellent riding comfort prepared by a novel polypropylene glycol. Polymer Journal, 40(9), 842-845.

  • Wei, L., & Griffin, J. (1998). The prediction of seat transmissibility from measures of seat impedance. Journal of Sound and Vibration, 214(1), 121-137.

  • Whitham, E. M., & Griffin, M. J. (2010). Measuring vibration on soft seats. In 1977 International Automotive Engineering Congress and Exposition (pp. 1-12). SAE International in United States.

  • Zhang, L., & Dupuis, R. (2011). Measurement and identification of dynamic properties of flexible polyurethane foam. Journal of Vibration and Control, 17(4), 517-526.

  • Zhang, X., Qiu, Y., & Griffin, M. J. (2015). Transmission of vertical vibration through a seat: Effect of thickness of foam cushions at the seat pan and the backrest. International Journal of Industrial Ergonomics, 48, 36-45.

ISSN 0128-7680

e-ISSN 2231-8526

Article ID


Download Full Article PDF

Share this article

Related Articles